1. Technical Field Text
The invention relates to vehicular selective catalyst reduction systems. In particular, the invention relates to managing the heat provided to the selective catalyst reduction system in a vehicle.
2. Background Information
Emission control for engines burning carbon based fuel is of great interest. Such interest exists for emission control for diesel compression piston engines commonly installed in off-highway earth moving equipment, for example an off-highway mining dump truck. Study of emission control has increased as many government agencies have issued deadlines for implementing emission control solutions that comply with guidelines. One solution under implementation by engine and equipment manufacturers is the use of selective catalyst reduction (hereinafter “SCR”). A subset group of SCR systems uses a liquid urea solution known as diesel exhaust fluid to support the catalytic reaction. The performance of the catalytic reaction within SCR systems is very heat dependent, requiring certain components of the SCR system to remain within specific temperature ranges that will allow the components of the SCR system to perform the catalytic reaction effectively. As the diesel exhaust fluid is injected in dosed measurement amounts, its proper function is highly dependent on subsequent heat available in the exhaust gases flowing to the catalyst components in the system.
Malfunction and poor reaction efficiency of SCR systems and components occurs when the heat provided by exhaust gases of the engine are insufficient for supporting the SCR system catalytic reaction process. SCR system components, such as valves, nozzles, injectors, and agents, may cease to function properly if the exhaust gas heat is insufficient. These low temperatures in turn also contribute to reduction of the functional life of certain components in the SCR system. Providing sufficient temperatures within the SCR system is normally met under the conditions of a working loaded engine due to the relatively high fuel usage rate in relation to the range of fuel usage rate for the specific engine. However, there exist time periods where idle or minimal engine power output are required for the vehicle operating condition. These time periods of minimal engine power provide conditions where low fuel usage rates exist, which in turn results in insufficient heat for acceptable SCR system operation. The insufficiency of heat increases as ambient temperatures decrease. Therefore, there is a need for a method and system to manage the heat provided to SCR systems.